Silicone pressure-sensitive adhesives (hereinafter also referred to as PSAs) typically contain at least two primary components, namely a linear siloxane polymer and an MQ resin consisting essentially of triorganosiloxane (M) units (i.e., R.sub.3 SiO.sub.1/2 units, in which R denotes a monovalent organic group) and silicate (Q) units (i.e., SiO.sub.4/2 units). In addition to the above two ingredients, silicone PSA compositions are generally provided with some crosslinking means in order to optimize various properties of the final adhesive product. And, in view of the high viscosity imparted by the polymer component, these PSA compositions are typically dispersed in an organic solvent for ease of application.
When such silicone PSA compositions employ an alkenyl-functional polymer and a crosslinking agent containing silicon-bonded hydrogen atoms, they can be cured by a hydrosilation addition reaction therebetween using a platinum-type catalyst. In such systems, the molar ratio of silicon-bonded hydrogen groups to silicon-bonded alkenyl groups is typically greater than 1, as exemplified by the disclosure of U.S. Pat. No. 4,988,779 to Medford et al. Although many of these PSAs have good adhesive properties, they often lack a balance between aggressive adhesion to substrates, such a metal, and high initial tack. A major drawback of such systems is that they tend to fail in a cohesive mode when peeled from a substrate, particularly when the peel rate is high. This has the untoward effect of transferring some of the adhesive to the substrate from which it is peeled (i.e., small "islands" of PSA remain on the substrate after the PSA is delaminated therefrom). This is highly undesirable in many commercial applications (e.g., in electronic masking applications do not want PSA residue left on components).